1. Field of Invention
The invention relates to a photosensitive member cartridge and a process cartridge for use in an electrostatographic image forming apparatus.
2. Description of Related Art
Some electrostatographic image forming apparatus in which a visible image is obtained by supplying toner to an electrostatic latent image formed on a photosensitive drum, are disclosed in, for example, Japanese Patent Publication Nos. 8-54786 and 9-319285, which correspond to U.S. Pat. Nos. 5,845,176 and 5,805,959, respectively.
The former publication discloses such structures that a photosensitive member cartridge including a photosensitive drum, and a developer cartridge including a developing roller, are separately set in a housing.
The latter publication discloses such structures that a photosensitive member cartridge and a developer cartridge are movably connected at one portion by a pin, so that a photosensitive member and a developing roller press against each other.
Generally, the surface of the photosensitive drum is coated with a light-sensitive material. To prevent the surface of the photosensitive drum from being scratched or contaminated, some measures need to be taken. Otherwise, when a portion of the photosensitive surface is scratched or contaminated with, for example, dust, such as would be caused by touching the surface of the photosensitive drum by hand, the photosensitive characteristics of the photosensitive surface are changed. Consequently, the image quality is adversely affected.
Accordingly, a well-known structure, in which the photosensitive drum is covered with a shutter, is employed for apparatus, such as those disclosed in the above-described publications.
However, the shutter needs to be constructed so as to open when the photosensitive member cartridge is set in a body (housing), and so as to close when the photosensitive member cartridge is removed from the body (housing). This makes the structure of the photosensitive member cartridge complicated. In addition, the possibility arises that a user may accidentally open the shutter and touch the surface of the photosensitive member cartridge.
Further, when the photosensitive member cartridge is placed on a table, the shutter may accidentally open, so that the photosensitive drum may be exposed.
One aspect of the invention is to provide a photosensitive member cartridge that obviates the danger of contamination or scratches on a photosensitive member. To achieve this aspect, the photosensitive member cartridge of the invention includes a case, and a photosensitive member and a transfer roller which are rotatably disposed in the case. The case covers the photosensitive member and the transfer roller. Specially, a bottom wall of the case covers a lower portion of the transfer roller, and upper and rear walls cover the photosensitive member.
The bottom wall extends below the transfer roller. On the extending portion of the bottom wall, a developer cartridge, including a developing roller, is set. Such structures prevent the photosensitive member and the transfer roller from being accidentally touched, which enhances image quality.
Also, it is unnecessary to provide complicated components such as a shutter, so that the structures of the photosensitive member cartridge are simplified.
Further, foot portions provided on the underside of the bottom wall stabilize the photosensitive member cartridge when it is placed on a table.